浅いV切欠きをもつ大型構造要素の脆性破壊強度評価へのローカルアプローチの適用 : 破壊制御設計へのローカルアプローチの展開(第5報)

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This paper employs the Local Approach for the evaluation of the fracture performance of a large structural component. The material used is a high strength steel of 490MPa class for steel-framed structures. Hollow-section beam specimens are constructed, where shallow V-notches are introduced at the edge of the flange. Conventional fracture mechanics procedures can not be directly applied to the notched component, because they have a basis on a crack or a crack-like defect. Three-dimensional FE-analysis demonstrates that the shallow V-notched component holds a considerably relaxed stress field compared to the fracture toughness specimen with a deep crack. This is due to a large difference in the near crack/notch tip constraint between the component and toughness specimen. This study insists that the Weibull stress, an integrated stress over the fracture process zone, is a measure of the fracture driving force of both notched and cracked specimens. The fracture load and fracture strain for the hollow-section beam with shallow V-notches can be predicted from the fracture toughness test results based on the Weibull stress criterion ; the critical Weibull stress at brittle fracture initiation is a material property regardless of the type of a notch/crack.